I tried setting IL2CPP as the builder and exporting but it only exports the x86 and ARM v7 native libs. Is it possible to export a Unity 5.3 project as an Android Studio project with ARM v8 jni libs bundled?
No, it is not possible for export a Unity project for ARMv8 on Android now. This is something that will be added in the future, but we're not sure when yet. For now, only 32-bit is supported.